Lhermitte phenomenon is a neurological symptom described as a sensation of electric shock that radiates from the back towards the extremities, which appears when a patient flexes the neck. A transient myelopathy as a late complication of radiotherapy is associated with this symptom. It appears two to four months after treatment and disappears spontaneously. We report a 45 years old female with a neck malignant melanoma treated with surgery and adjuvant radiotherapy. She experienced the Lhermitte phenomenon that was triggered by heat. This phenomenon must be differentiated from the Uhthoff phenomenon.